1. Field of the Invention
The present invention relates to a liquid discharging head which discharges a desired liquid by generating bubbles with thermal energy or the likes a method for manufacturing liquid discharging head, and a liquid discharging apparatus, and particularly relates to a liquid discharging head using a movable separation film which is displaced using the generation of bubbles.
Note that with the present invention, the term xe2x80x9crecordxe2x80x9d refers not only to applying meaningful images such as characters or shapes to recording media, but also to applying images without any particular meaning, such as patterns, to recording media
Also, with the present invention, the term xe2x80x9cnot yet drivenxe2x80x9d refers to the state of an article which is to be sequentially driven, but the time for this article to be driven has net yet come.
2. Description of the Related Art
There conventionally is known the so-called bubble jet recording method which is an ink-jet recording method wherein, with a recording device such as a printer or the like, energy such as thermal energy or the like is applied to liquid ink in a channel to cause bubbles therein, thereby discharging ink from discharging orifices due to an operating force based on the sudden change in volume due to the bubbles generated, the discharged ink adhering to a recording medium to form images. As disclosed in U.S. Pat. No. 4,723,129, recording apparatuses using this bubble jet recording method generally comprise discharging orifices for discharging ink, channels connecting to the discharging orifices, and electro-thermal converters serving as energy generating means for discharging ink disposed within the channels.
According to such a recording method, high-quality images can be recorded a high speed with little noise, and also, and the discharge orifices for discharging ink can be arrayed at high density with heads for this recording method, so this method is advantageous in many ways, such as yielding high-resolution recorded images with small apparatuses and also facilitating color image recording. Accordingly, in recent years, bubble jet recording devices have come to be used with many sorts of office equipment, such as printers, photocopiers, facsimile devices, and so forth, and even with industrial systems such as textile printing machines.
As bubble jet technology has come to be used in products in various fields, various types of demands have come to be made, as described next.
Driving conditions for providing liquid discharging methods or the like whereby suitable ink discharge based on stable bubble generation can be provided with high-speed ink discharging have been proposed, and improved channel shapes for obtaining liquid discharging heads with fast refilling speed (i.e., channels which have discharged ink are speedily refilled with ink for the next discharge) from the perspective of high-speed printing, have been proposed, in order to obtain high-quality images.
In addition to such heads, an invention has been disclosed in Japanese Patent Laid-Open No. 6-31918, which takes note of back waves (pressure directed toward the opposite direction of the discharge orifices) generated at the time of generating bubbles, and provides a structure which prevents back waves which are lost energy in the discharging action. The invention disclosed here has a triangular portion of a triangular plate member facing a heater which generates bubbles with this invention, the back waves can be temporarily suppressed, though slightly, with the plate member. However, no mention whatsoever is made of the relation between growth of the bubble and the triangular portion, and no thought has been given thereto, so the above invention has the following problems.
That is to say, with the invention disclosed in the above publication, the heater is situated at the base of a recess and there is no linear connection state with the discharging orifice, so the droplet form is unstable, and further growth of the bubble is permitted from around the apex portion of the triangle, so the bubble grows from one side of the triangular plate member to the other side, i.e., over the entirety, and consequently a normal bubble grows to its full size in the liquid as if the plate member did not even exist. Accordingly, the plate member is unrelated to the grown bubble. Conversely, the entirety of the plate member is surmounted by the bubble, is in the stage of the bubble shrinking, disturbances are generated in the process of refilling ink to the heater situated in the recess, resulting in minute bubbles being accumulated therein, and eventually disturbing the principle of discharge based on growing bubbles itself.
Next, EP Patent Laid-Open No. 436047A1 discloses an invention wherein a first valve is disposed between the discharge orifice area and the bubble generating portion for closing these off, and a second valve is disposed between the bubble generating portion and the ink supplying portion for completely closing these off, the first and second valve being alternately opened and shut (FIGS. 4 through 9 in EP 436047A1). However, this invention sections these three chambers into two each, so at the time of discharging the ink following the droplet causes massive tailing, so the number of satellite dots is far greater than with a normal discharge method which performs bubble growth, reduction, and dissipation (it is assumed that meniscus regression during to dissipation of the bubble will not be usable). Also, at the time of refilling, the liquid is supplied to the bubble generating portion as the bubble dissipates, but liquid cannot be supplied to the discharging orifice area until the next bubble generation starts, so not only are the irregularities in discharged liquid droplets great, but also the discharge response frequency is extremely great, and accordingly this invention is not at a practical level.
On the other hand, the present assignee has proposed many inventions using movable members (plate-shaped members having a free end closer to the discharge orifice side than the fulcrum) which are completely different from the above-describe conventional art and effectively contribute to discharging of liquid droplets. Of such inventions, Japanese Patent Laid-Open No. 9-48127 discloses an invention wherein the upper limit of displacement of the moving member is restricted, in order to prevent slight disturbance in the behavior of the aforementioned movable member. Also, Japanese Patent Laid-Open No. 9-323420 discloses an invention wherein the position of the common liquid chamber upstream from the movable member is shifted toward the free end side of the movable member using the advantages of the movable member, i.e., shifted downstream, thereby increasing the refilling capability. These inventions were based upon the conception of temporarily enveloping the growth of the bubble with the movable member and then from that state discharging the bubble all at once toward the discharging orifice side, and accordingly, various individual elements relating to formation of droplets by the entire bubble and relations thereof were not noted.
As a next stage, the present assignee has disclosed in Japanese Patent Laid-Open No. 10-24588 an invention wherein a part of the bubble generating area is released from the movable member, as an invention taking note of bubble growth due to pressure wave propagation (acoustic wave) as an element relating to liquid discharge. However, this invention also only focuses on the growth of the bubble at the time of discharging liquid, and accordingly various individual elements relating to formation of droplets by the entire bubble and relations thereof are not noted.
While it is known that the front portion of bubbles (edge shooter type) with conventionally-known film boiling greatly affects discharging, there have conventionally been no inventions taking note of using this portion to effectively contribute to formation of discharging droplets, so the present inventors have diligently studied this matter to reach a technological solution.
Further the present inventors took notice of the displacement of the movable portion and generation of the bubble, and eventually reached the following useful understanding.
That understanding is to restrict the displacement of the free end as to the growth of the bubble with a stopper for the movable member, which is a displacement restricting member of the movable member. Restricting he displacement of the movable member with the stopper restricts the bubble from growing in the upstream side of the channel, so energy for discharging the liquid is effectively transferred to the lower side where the discharge orifice is formed.
FIG. 14 shows a side view of an example of an edge-shooter type liquid discharging head having a stopper.
A device substrate 301 having a heat-generating member 310 which is the bubble generating means and a movable member 311, a top plate 302 having formed thereupon a stopper 312 with the rear side thereof extended in the upstream direction, and an orifice plate 305 having discharging a discharging orifice 304 formed therein, are provided.
The channel 303 through which the liquid flows is formed by the device substrate 301 and the top plate 302 being fixed in a layered manner. Also, multiple channels 303 are arrayed for one liquid discharging head, connecting to the discharging orifices 304 for discharging liquid formed downstream (to the left side in FIG. 13). A bubble generating area exists near the area of the face where the heat-generating member 310 and the liquid come into contact. Also, a great-capacity common liquid chamber 306 is provided in the upstream direction of each channel 303 (to the right side in FIG. 13), so as to connect simultaneously. In other words, the channels 303 are formed so as to branch off of the single common liquid chamber 306. The height in the liquid chamber of this common liquid chamber 306 is formed so as to be higher than the height in the channel of the channels 303.
The movable member 311 is of a cantilever type supported at one end, fixed to the device substrate 301 at the upstream side of the flow of ink, and is vertically free to move as to the device substrate 301 at the portion further downstream from a fulcrum 311a. In the initial state, the movable member 311 is positioned generally parallel to the device substrate 301 while maintaining a gap with the device substrate 301.
The movable member 311 disposed on the device substrate 301 is positioned such that the free end 311b is situated at approximately the center area of the heat generating element 310. Also, the stopper 312 provided to the top plate 302 restricts the amount of displacement of the free end 311b in the upwards direction by the free end 311b of the movable member 311 coming into contact with the stopper 312. At the time that the amount of displacement of the movable member 311 is restricted by the movable member 311 coming into contact with the stopper 312 (i.e., in the event that the movable member is in contact), the channel 303 is essentially closed off between the movable member 311 and stopper 312 on upstream, and the movable member 311 and stopper 312 on downstream, by the movable member 311 and the stopper 312.
Next, FIG. 15 shows each of the movable members in the state of coming in contact with their stoppers, at the time of discharging ink.
The free end 311b of the movable member 311 is displaced upwards by the generated bubble 340 at the time of discharging ink, and comes into contact with the stopper 312. In the event that the bubble 340 further grows in the state that this free end 311b is in contact with the stopper 312, the movable member 311 warps toward the top plate 302, and deforms into a convex shape.
Now, in the event that multiple heat-generating members are formed on such as liquid discharging head, energy is not simultaneously applied to multiple heat-generating members, but rather the block driving method is used, wherein the heat-generating members are separated into multiple blocks made up of heat-generating members which discharge at approximately the same time, and the heat-generating members are driven in units of blocks. This is performed to prevent efficiency from suffering due to applying electric signals to all heat-generating members at the same time which would increase the current flowing simultaneously and require a power source capable of supplying a great current, and also to prevent efficiency from deteriorating due to voltage from the power source dropping between heat-generating member lines.
However, in the event that driving is performed by block driving with a liquid discharging head having the above movable members and stoppers, there has been a problem in that a first discharging droplet 350 discharged from a nozzle 371 near the boundary is smaller than other discharged droplets, and also the discharging speed is slow, thereby sometimes resulting in recording irregularities, as shown in FIG. 15. This FIG. 15 is a diagram schematically illustrating the amount of ink discharged and the discharging speed, and represents that while originally ink is not simultaneously discharged from the leading driving nozzle 351 and the near-boundary nozzle 371, ink is being simultaneously discharged from the leading driving nozzle 351 and the near-boundary nozzle 371.
The present inventors studied the case of deterioration in the discharging amount and the discharging speed at the near-boundary nozzles, and found that this is a phenomena unique to liquid discharging heads having the above movable members and stoppers. That is, this occurs due to the fact that the force for drawing surrounding ink into the nozzle at the time of the bubble dissipating is far greater with liquid discharging heads having the movable members and stoppers as compared to conventional heads. As shown in FIG. 16, this is supposed to be due to the amount of ink within the near-boundary nozzle 371 at the time of driving this near-boundary nozzle 371 decreasing, since following dissipation of the bubble in the leading driving nozzle 351, filling of ink is attempted not only from the common liquid chamber 306 but also from the nozzles at the boundary of the trailing driving block 370 that has not been driven and from the near-boundary nozzle 371 thereof, situated at the boundary and near the boundary with the block that has been driven.
The present invention has been made in light of the above problems, and accordingly it is an object thereof to provide a liquid discharging head, a method for manufacturing liquid discharging head, and a liquid discharging apparatus, wherein recording irregularities, due to liquid being drawn in from adjacent channels, are suppressed.
To this end, the liquid discharging head according to the present invention comprises: a plurality of heat-generating elements for generating thermal energy for generating bubbles in a liquid; a plurality of discharging orifices corresponding to each of the heat-generating elements, whereby the liquid is discharged; a plurality of channels connecting to the discharging orifices and having bubble generating areas for generating bubbles in the liquid; a plurality of movable members provided in the bubble generating areas so as to corresponding to each of the heat-generating elements, each having a free end which is displaced in accordance with growth of a bubble; a plurality of restricting portions provided in the channels so as to correspond to each of the movable members, for restricting the amount of movement of the movable members; and a common liquid chamber connected to each of the channels, for supplying liquid to each of the channels; wherein the heat-generating elements are sectioned into a plurality of blocks for each of the heat-generating elements discharging ink in a generally simultaneous manner, the heat-generating elements are sequentially driven in time-division in increments of the blocks, and the liquid is discharged from the discharge orifices by the energy of the bubbles being generated and wherein each of the restricting portions comprise a plurality of a first restricting portion and at least one second restricting portion having a shape such that the fluid resistance of liquid from the discharging orifice side toward the common liquid chamber is greater than the fluid Resistance generated at the first restricting portion.
With the liquid discharging head according to the present invention configured as described above, the second restricting portion, where fluid resistance of liquid from the discharge side to the common liquid chamber is greater than the fluid resistance of the first restricting portion, suppresses liquid in channels not driven, from being drawn out under the effects of refilling channels having heat-generating members that have been driven, and accordingly, meniscus regression formed at discharging orifices connecting to channels having second restricting portions can be restricted.
Also, each second restricting portion may be contained in a trailing driving block which is adjacent to a leading driving block which is the block that is driven first, and driven later than the leading driving block, and be disposed within the channel positioned adjacent to the boundary between the leading driving block and the trailing driving block. In this case, meniscus regression formed at discharging orifices connecting to channels positioned at the boundary between the leading driving block and the trailing driving block which is most readily affected by the refilling of the leading driving block, can be particularly effectively suppressed by forming a second restricting portion in channels positioned adjacent to this boundary.
Each of the second restricting portions may be greater in dimensions that the first restricting portion.
The liquid flow direction length of each restricting portion which is the length in the direction which the liquid flows through the channel may be longer for the second restricting portion than for the first restricting portion, the frontal projection area of each restricting portion in the direction which the liquid flows through the channel may be greater for the second restricting portions than for the first restricting portions, and further the spacing between the second restricting portion and a wall face forming the channel may be narrower than the spacing between the first restricting portion and a wall face forming the channel.
Also, each of the restricting portions may contain at least a third restricting portion which has a greater fluid resistance than the first restricting portion and a smaller fluid resistance than the second restricting portion, disposed within the channel positioned adjacent to the channel wherein the second restricting portion is disposed.
The method for manufacturing a liquid discharging head according to the present invention comprises: a plurality of channels formed by joining an essentially flat substrate having a plurality of movable members corresponding to each of a plurality of heat-generating elements for generating thermal energy for generating bubbles in a liquid, the movable members each having a free end which is displaced in accordance with growth of a bubble, with a top plate formed with a groove portions having a plurality of restricting portions corresponding to each of the movable members, for restricting the amount of displacement of the movable members, the plurality of channels connecting to a plurality of discharging orifices for discharging the liquid and having bubble generating areas for generating bubbles in the liquid; and a common liquid chamber connected to each of the channels, for supplying liquid to each of the channels; wherein the heat-generating elements are sectioned into a plurality of blocks for each of the heat-generating elements discharging ink in a generally simultaneous manner, the heat-generating elements are sequentially driven in time-division in increments of the blocks, and the liquid is discharged from the discharge orifices by the energy of the bubbles being generated; wherein the method comprises a step for forming the top plate such that each of the restricting portions comprise a plurality of a first restricting portion and at least one second restricting portion having a shape such that the fluid resistance of liquid from the discharging orifice side toward the common liquid chamber is greater than the fluid resistance generated at the first restricting portion.
With the method for manufacturing the liquid discharging head according to the present invention configured as described above, a liquid discharging head can be manufactured wherein the second restricting portion, where fluid resistance of liquid from the discharge side to the common liquid chamber is greater than the fluid resistance of the first restricting portion, suppresses liquid in channels not driven, from being drawn out under the effects of refilling channels having heat-generating members that have been driven, and accordingly, meniscus regression formed at discharging orifices connecting to channels having second restricting portions can be restricted.
Also, the method for manufacturing the liquid discharging head according to the present invention may further comprising a step wherein each of the second restricting portions contained in a trailing driving block which is adjacent to a leading driving block which is driven first, and driven later than the leading driving block, is formed within the channel positioned adjacent to the boundary between the leading driving block and the trailing driving block.
The method may further comprise a step wherein each of the second restricting portions is formed greater in dimensions that the first restricting portion.
Further, the method for manufacturing a liquid discharging head according to the present invention may further comprise a step for forming the second restricting portion such that the liquid flow direction length of each restricting portion which is the length in the direction which the fluid flows through the channel is longer for the second restricting portion than for the first restricting portion, or a step for forming the second restricting portion such that the frontal projection area of each restricting portion in the direction which the fluid flows through the channel is greater for the second restricting portion than for the first restricting portion, or a step for forming the second restricting portion such that the spacing between the second restricting portion and a wall face forming the channel is narrower than the spacing between the first restricting portion and a wall face forming the channel.
Also, the method for manufacturing a liquid discharging head according to the present invention may further comprise a step for forming for each of the restricting portions at least one third restricting portion which has a greater fluid resistance than the first restricting portion and a smaller fluid resistance than the second restricting portion, disposed within the channel positioned adjacent to the channel wherein the second restricting portion is disposed.
The liquid discharging apparatus according to the present invention comprises: a liquid discharging head according to the present invention; and a control unit for controlling sequential driving of the blocks.
The liquid discharging apparatus according to the present invention, configured as described above, has a liquid discharging head wherein the second restricting portion, where fluid resistance of liquid from the discharge side to the common liquid chamber is greater than the fluid resistance of the first restricting portion, suppresses liquid in channels not driven, from being drawn out under the effects of refilling channels having heat-generating members that have been driven, and accordingly, meniscus regression formed at discharging orifices connecting to channels having second restricting portions can be restricted, so discharging irregularities due to meniscus regression can be suppressed.
The liquid discharging apparatus according to the present invention may comprise medium transporting means for transporting a recording medium for receiving liquid discharged from the liquid discharging head, and may record by discharging ink from the liquid discharging head so that ink adheres to the recording medium.